The invention related to a device that determines characteristics of fluids, by first measuring variations in the fluid's electrical resistance, translucence, sonic properties, over a range of temperatures or time or both, then by transmitting the generated information to a data logger and computer, where the information is compared to standard curves. This equipment can be made fully portable, so that it can be taken to locations away from laboratories, and has obvious applicability in oilfield applications. The invention further relates to a method for selecting chemicals to modify the fluid's measured characteristics.
Systems carrying oil field production fluids, refinery fluids, and other industrial fluids, containing either an oil or water phase, or both, are susceptible to various chemical related problems, including emulsion formation, wax deposits, scale formation, and asphaltene deposits, in either static or dynamic systems. Entire laboratories are devoted to the evaluation of, and treatment of these problems to reduce their economic impact on the systems. Many of these laboratories have large numbers of highly trained specialists, very expensive scientific equipment, and require large budgets to operate.
Emulsions are complex surface phenomena which results from the interaction of naturally occurring surfactants in multi-component physical systems. Emulsions can be formed as water-in-oil, or oil-in-water mixtures, and the internal phase droplets can range in size from 50 microns, to 0.05 microns. The most stable emulsions have droplets of smaller size. Naturally occurring surfactant which stabilize the emulsion include, but are not limited to, fatty acids, naphthinic acids, fatty organic salts, and other break-down products of bio-molecules.
Emulsions are not desirable in oilfield production, as the purchasers of the production want to purchase oil without any water. Hence, emulsions are treated on-site to separate the water from the oil. Emulsions can be de-stabilized by the addition of synthetic surfactant, salts, or heat; dilution of the water or oil phase; and the use of electro-static grids. Typical demulsification testing is done empirically, by adding various additives to samples of the emulsion, agitating, and then visually observing the amount of water separated from the emulsion through a set amount of time. In the case of the oil-in-water emulsion, a turbidimeter may be used. Demulsification testing is notorious because of the difficulty in generating consistent test results, as all samples are manipulated by hand, and all measurements made by visual observation.
Natural oils, petroleum crude oils, and animal derived oils often contain waxes. Waxes tend to crystallize in these oils when the temperature drops below their respective melting points. These crystallized waxes lose their solubilities in the oil, and network to create larger aggregates which can solidify or gel the oil, or the wax crystals precipitate from the oil. These crystals often form deposits in the system in which they are contained, and cause various physical and mechanical problems (e.g., deposition of solids in storage tanks, deposits in transfer lines, solidification or gelling of the oil, pipeline ruptures due to overpressurization, etc.). Wax problems may be corrected with the use of dispersants, crystal modifiers, or combinations of each. Testing used to determine the extent of the problem and to test possible beneficial additives is performed empirically using rheological analysis, pour point testing (ASTM D-97), cloud point testing, cold finger testing, and other physical-chemical tests, with the tester trying any number of possible additives and visually observing the changes in the sample. Obviously, the tester cannot be sure he has selected the optimum product by this method unless he tests all possible additives, which can be a time-consuming process.
Scale deposition in non-homogeneous systems (e.g., oil-in-water emulsions, and water-in-oil emulsions) does occur, and scale deposition also occurs in high brine, water-only systems. Scale testing may be conducted by several methods, but the most common methods involve the heating of fluids from the field or synthetically produced approximations and measuring the deposits formed. Once the scale crystals are formed, the specific scale can be identified by methods such as X-ray crystallography or atomic absorption. Scale problems may be treated using inorganic salts, polymeric acids, or phosphate esters, which can interfere with the normal crystallization process of the scale crystals.
Asphaltenes are complex, hetero-atomic, polar, macrocyclic, compounds containing carbon, hydrogen, sulfur and oxygen. Asphaltenes occur in crude oils. Resin and maltene precursors of the asphaltenes act as peptizing agents in virgin crude oils to stabilize a dispersion of micelles. When mechanical or chemical forces become sufficiently great, these stabilizing species are lost and the destabilized asphaltenes become susceptible to interaction and aggregation resulting in deposition of asphaltene macro-particles. Testing for asphaltenes, is most effectively accomplished by core tests, in which a suspension of the asphaltenes are pumped through a core-rock sample, and pressure build-up measured. Xylene, toluene or other aromatic solvents have been used for many years for the removal of asphaltenes.
The invention disclosed herein is a testing device capable of determining key fluid characteristics under a variety of controlled conditions. This invention also includes an improved method for selecting treatment additives, utilizing the inventive device.